I. Field of the Invention
The present invention relates generally to a loader/unloader system for use with an industrial machine, such as a hemming machine.
II. Description of the Prior Art
Many industrial machines, such as hemming machines, include a work station adapted to receive an unmachined part whereupon the machine performs its particular machining operation. Following the machining operation, the now machined workpiece is removed from the work station and replaced by an unmachined workpiece whereupon the entire operation is repeated.
Most industrial applications utilize both a loader robot for moving unmachined parts from inventory and into the work station on the machine. Similarly, an unloader robot is then utilized to remove the finished workpieces following the machining operation from the work station. Typically, conventional conveyor systems supply the loader robot with unmachined workpieces while, similarly, conventional conveying systems remove the machined workpieces from the unloader robot.
It is, of course, imperative that the loader robot avoid collision, or any possible collision, with the unloader robot at all times. Any such collision between the loader and unloader robots, or the parts which they transport, would result in damage not only to the workpieces transported by the loader and/or unloader robots, but also potentially damage the robots themselves.
Consequently, it has been the previously known practice to program both the loader and unloader robots to avoid collision with each other by sequentially interlocking the motion of each robot to avoid interference and conflicts. This robot sequencing in the time results in a time delay of several seconds sufficient to terminate operation of either the loader or unloader operation in the event of a system jam or other malfunction and still avoid a collision between the loader and unloader robots.
The previously known practice of utilizing loader and unloader robots for a machining operation, such as a hemming operation, suffers from two primary disadvantages. One disadvantage is that the loader and unloader robots are expensive both in acquisition and operating costs. Furthermore, the necessity of having both a separate loader robot and unloader robot for each machine significantly increases the overall cost of performing the machining operation.
A still further disadvantage of these previously known loader and unloader robotic systems is that the part exchange operation necessarily consumes several seconds more than an unflexible transfer system, typically about five seconds, after each machining operation to ensure that the loader and unloader robots do not collide together. This, however, necessarily lengthens the cycle time for the machining operation by several seconds. Since each machining operation may itself only consume twelve to sixteen or thirty seconds, the addition of five seconds to each machining cycle effectively increases the cycle time up to 30%.
The present invention provides a loader/unloader system for a machine which overcomes all of the above-mentioned disadvantages of the previously known systems.
In brief, the present invention provides a workpiece loader/unloader system for an industrial machine, such as a hemming machine, in which the industrial machine has a work station adapted to receive unmachined workpieces. Once the unmachined workpiece is positioned at the work station, the industrial machine undergoes a machining operation thus forming a machined workpiece.
The loader/unloader system comprises a shuttle which is movable between an extended position and a retracted position. In its extended position, the shuttle overlies the work station. Conversely, when the shuttle is in its retracted position, the shuttle is laterally spaced from the work station.
At least one gripper is mounted to the shuttle and selectively engages and supports the workpiece after the workpiece has been machined at the work station. Preferably, the gripper includes at least two fingers which, when in their engaged position, extend underneath the workpiece following a machining operation at the work station.
A loader manipulator is movable between a preload position and a load position. In its preload position, the loader manipulator supports an unmachined workpiece at a position laterally spaced from the work station. Conversely, at its load position, the loader manipulator overlies the work station and selectively positions the unmachined workpiece into the work station of the machine.
Unlike the previously known loader/unloader systems, however, the loader manipulator includes a pin which mechanically engages the slot in the shuttle when the loader/manipulator is positioned at a preload position, i.e. laterally spaced from the work station. Then, as the loader manipulator is moved to its loader position in which the loader manipulator with its unmachined workpiece overlies the work station, the loader manipulator simultaneously mechanically pushes the shuttle laterally from its extended position and to its retracted position.
With the shuttle at its retracted position, a retaining pin engages the shuttle and holds the shuttle at its retracted position. The finished workpiece which is carried by the shuttle is then removed from the shuttle in any conventional fashion. During the removal of the workpiece from the shuttle, however, the loader manipulator disengages from the shuttle and is moved to acquire a new unmachined workpiece.
After the machined workpiece is removed from the shuttle, the retaining pin is retracted and preferably a passive means such as a spring, or an active means such as an air cylinder, returns the shuttle to its extended position so that the shuttle overlies the machine work station. The grippers on the shuttle are then opened, the completed or machined workpiece positioned within the shuttle, and the grippers are then moved to their engaged position. At that time, the loader manipulator with its new unmachined workpiece mechanically engages the shuttle whereupon the above process is repeated.
Unlike the previously known loader/unloader systems, since the loader manipulator is utilized not only to load unmachined workpieces into the work station but also to mechanically move the shuttle with its completed or machined workpiece laterally away from the workstation, the previously known inclusion of several seconds to avoid collision between the loader robot and unloader robot is completely avoided. Indeed, mechanical contact between the loader manipulator and the shuttle assembly occurs during each machining cycle.
A still further advantage of the present invention is that, since the loader manipulator is used not only to load unmachined parts into the work station but also to mechanically push the shuttle with its completed workpiece away from the work station, only a single robotic manipulator is required to perform both the load and unload operations. This, in turn, significantly reduces the overall cost of the loader/unloader system.